The present invention relates to a thermal spraying method using a computer for automatically determining spray conditions on the basis of data on a thermal spray material and the shape of a workpiece to be subjected to thermal spraying, and a thermal spraying robot system for carrying out the thermal spraying method.
It is an imperative problem to keep the inlet temperature of a gas turbine at temperatures not lower than 1300xc2x0 C. to improve the power generating efficiency of a gas-turbine power plant. Efforts have been made to enhance the refractory quality of liners and transition pieces for combustors, vanes and blades, which are exposed to a high-temperature gas, to solve such a problem, and it is urgently necessary to develop heat-resistant materials, i.e., heat-resistant alloys. The withstandable temperatures of state-of-the-art heat-resistant alloys are 850xc2x0 C. at the highest. Presently available heat-resistant alloys are not necessarily satisfactory particularly in respect of resistance to high-temperature oxidation and high-temperature corrosion.
Technique intended to deal with raising the inlet temperature of gas turbines coats the surfaces of parts with a ceramic material having a small conductivity by thermal spraying. This technique is called thermal barrier coating (hereinafter abbreviated to xe2x80x9cTBCxe2x80x9d). TBC has effect on suppressing substantial rise in the temperature of alloy materials. The effect in thermal insulation of TBC is considered to lower the temperature of member by a temperature in the range of 50 to 100xc2x0 C.
TBC has been applied to combustors and transition pieces used in gas turbine power plants. However, heat insulating ceramic materials have values of physical properties greatly different from those of heat-resistant alloys, which causes the separation of coating layers from base metals. To solve such a problem and to enhance the reliability of parts, homogeneous coating films having high adhesion must be formed.
When coating the inner surfaces of liners of combustors or the inner transition pieces by thermal spraying, the shapes of the liners and the transition pieces place restrictions on thermal spraying and hence it is difficult to carry out thermal spraying without changing the distance between a spraying gun and a workpiece, and the inclination of a spraying gun to the surface of a workpiece and, consequently, it is difficult to form satisfactory coatings over the surfaces of workpieces. To solve such a problem, trials have been made to control a spraying gun automatically by a robot. Teaching of a path for a thermal spraying gun for the shape of each workpiece is necessary to maintain the distance between the thermal spraying gun and the workpiece constant and to maintain the thermal spraying gun perpendicular to the surface of the workpiece throughout a thermal processing process. Therefore, the development of programs requires much time, and a new program must be developed for every new workpiece.
Accordingly, it has been desired to develop a thermal spraying robot system capable of automatically determining spraying conditions and a path for a thermal spraying gun suitable for the shape of every workpiece. However, as mentioned above, when processing the liners and transition pieces of combustors by thermal spraying, interference between the thermal spraying gun and a workpiece and the ability of a thermal spraying gun driving mechanism place many restrictions on thermal spraying to coat the inner surfaces of workpieces; that is, the distance between the thermal spraying gun and the workpiece and the angle of the thermal spraying gun to the workpiece cannot be kept in optimum ranges and the thermal spraying gun cannot be moved at a constant moving velocity. Any thermal spraying robot system capable of automatically determining spraying conditions according to the shape of the workpiece has not yet been provided because of such restrictions.
The present invention has been made in view of the foregoing circumstances and it is therefore an object of the present invention to provide a thermal spraying robot system capable of automatically determining spraying conditions according to the shape of a workpiece.
With the foregoing object in view, the present invention provides a thermal spraying robot system comprising an input unit for entering shape data on the shape of a workpiece and material data on a thermal spray material, a spray condition database storing values of a plurality of spray parameters dominating the qualities of sprayed coatings and corresponding to qualities of sprayed coatings for thermal spray materials, a path calculating unit for selecting values of the spray parameters stored in the spray condition database and calculating a path for a thermal spraying gun on the basis of the selected values of the spray parameters and the shape data on the workpiece, and a thermal spraying apparatus including the thermal spraying gun, for carrying out a thermal spraying operation on the basis of the selected values of the spray parameters and a path for the thermal spraying gun calculated by the path calculating unit.
The plurality of spray parameters include, as principal parameters, at least spray distance d between the workpiece and the thermal spraying gun, angle xcex8 between the thermal spraying gun and the workpiece and moving velocity v of the thermal spraying gun relative to the workpiece. The path calculating unit calculates a path for the thermal spraying gun on the basis of the selected values of the principal parameters.
The values of the plurality of spray parameters stored in the spray condition database include optimum values specifying optimum spray conditions, and allowable values specifying allowable spray conditions for providing sprayed coatings of allowable qualities inferior to qualities of sprayed coatings formed by thermal spraying under the optimum spray conditions. The path calculating unit selects the optimum values of the spray parameters at the beginning.
The path calculating unit changes the optimum value of at least one of the principal parameters for the allowable value when it is impossible to calculate a path for the thermal spraying gun on the basis of the optimum values of the principal parameters, and recalculates a path for the thermal spraying gun.
The path calculating unit changes the optimum values of the principal parameters excluding at least one of the principal parameters for the allowable values when it is impossible to calculate a path for the thermal spraying gun on the basis of the optimum values of the principal parameters, and recalculates a path for the thermal spraying gun.
The input unit further has a function to specify the principal parameter having the optimum value to be kept unchanged.
If it is impossible to calculate a path for the thermal spraying gun even if the optimum values of all the principal parameters are changed for the allowable values of the same, the path calculating unit uses values of the principal parameters other than the allowable values and recalculates a path for the thermal spraying gun by using the values of the principal parameters other than the allowable values.
The thermal spraying robot system further comprises a display means for displaying, when the optimum value of at least one of the plurality of principal parameters is changed for the allowable value, the principal parameter which has been adjusted, in which the input unit further has a function to determine whether or not thermal spraying is to be executed by using the changed principal parameter.
The present invention provides a thermal spraying method using a thermal spraying apparatus provided with a thermal spraying gun, and a computer for determining spray conditions, comprising: a data entering step of entering shape data on the shape of a workpiece and material data on a thermal spray material, selecting values of spray parameters corresponding to the entered material data on the thermal spray material from a spray condition database storing values of a plurality of spray parameters dominating qualities of sprayed coatings and corresponding to qualities of sprayed coatings for thermal spray materials, a path calculating step of calculating a path for the thermal spraying gun on the basis of the selected values of the spray parameters and the shape data on the workpiece according to a predetermined program, a decision step of deciding whether or not thermal spraying can be carried out by moving the thermal spraying gun along the calculating path, and a thermal spraying step of carrying out a thermal spraying operation on the basis of the selected values of the spray parameters and the calculated path for the thermal spraying gun.
The plurality of spray parameters include, as principal parameters, at least spray distance d between the workpiece and the thermal spraying gun, angle xcex8 between the thermal spraying gun and the workpiece and moving velocity v of the thermal spraying gun relative to the workpiece.
The values of the plurality of spray parameters stored in the spray condition database include optimum values specifying optimum spray conditions, and allowable values specifying allowable spray conditions for providing sprayed coatings of allowable qualities inferior to the qualities of sprayed coatings formed by thermal spraying under the optimum spray conditions. The optimum values of the spray parameters are selected at the beginning in the selecting step.
If it is decided in the decision step that it is impossible to carry out thermal spraying, the selecting step and the path calculating step are executed at least one cycle, and at least one of the values of the spray parameters selected in the second and the following cycles of the selecting step is an allowable value selected instead of the optimum value.
The present invention provides a product produced by coating a workpiece with a sprayed coating formed by a thermal spraying method using a thermal spraying apparatus having a thermal spraying gun and a computer for determining spray conditions, and comprising a data entering step of entering shape data on the shape of a workpiece and material data on a thermal spray-material, a selecting step of selecting values of spray parameters corresponding to the entered material data on the thermal spray material from a spray condition database storing values of a plurality of spray parameters dominating qualities of sprayed coatings and corresponding to qualities of sprayed coatings for thermal spray materials, a path calculating step of calculating a path for the thermal spraying gun on the basis of the selected values of the spray parameters and the shape data on the shape of the workpiece according to a predetermined program, a decision step of deciding whether or not thermal spraying can be carried out by moving the thermal spraying gun along the calculating path, and a thermal spraying step of carrying out a thermal spraying operation on the basis of the selected values of the spray parameters and the calculated path for the thermal spraying gun.
The workpiece is a combustor liner for a combustor or a transition piece included in a gas turbine power plant.
According to the present invention, spray conditions can selectively be determined for all kinds of shapes of workpieces without distinction between two-dimensional shapes and three-dimensional shapes, a path for the thermal spraying gun can be calculated and a thermal spraying operation can be carried out. The time necessary for the development of a thermal spraying program can be reduced.